Semiconductor laser and optical module

Abstract

In a horizontal cavity surface emitted laser, there is provided a device structure that is capable of obtaining a circular narrow-divergence emitted beam that is high in the optical coupling efficiency with a fiber. As a first means, there is provided a horizontal cavity surface emitting laser having a structure in which the plane mirror that is inclined by 45° and the bottom lens of the oval configuration are integrally structured. As a second means, there is provided a horizontal cavity surface emitting laser in which the mirror having the columnar front surface configuration inclined by 45° and the bottom lens of the columnar front surface configuration are integrally structured. Since the horizontal component and the vertical component of the laser beam can be shaped, independently, through the above means. As a result, it is possible to obtain the circular narrow-divergence emitted beam.

1. A semiconductor laser comprising:
 a semiconductor substrate; 
 an active layer formed on a main surface of the semiconductor substrate which generates light; 
 an optical waveguide for propagating the light that is generated from the active layer; 
 a resonant cavity structure for optical feedback along the propagation direction; 
 a mirror for reflecting the laser beam emitted from the cavity in a substrate rear surface direction; 
 and a lens having a curved semiconductor surface at the substrate rear surface side for emitting the laser beam reflected by the mirror, 
 wherein when the semiconductor substrate is in an xy plane of right-hand orthogonal coordinates, and the optical axial direction of the optical waveguide is in parallel to the x-axial direction, the normal direction to the mirror surface and the z-axial direction form an angle of 45°, and the laser beam is emitted in the substrate rear surface direction that is the negative direction of the z-axis, 
 wherein the outer peripheral configuration of the lens, as viewed from the substrate rear surface side, is an oval configuration that satisfies the following relationship:
     a   −2   x   2   +b   −2   y   2 =1 
 
 where a and b are a radius in the x-axial direction and a radius in the y-axial direction, respectively, and satisfies a relationship of a<b; 
 wherein a that represents the radius in the x-axial direction and b that represents the radius in the y-axial direction meets a relationship of 3 μm <a <b <200 μm. 
 
     
     
       2. The semiconductor laser according to  claim 1 ,
 wherein the mirror has a plane configuration, and 
 wherein the cross-sectional configuration of the lens in the y-axial direction has an oval curvature. 
 
     
     
       3. The semiconductor laser according to  claim 2 ,
 wherein the lens is configured as to project toward an outer side of the rear surface of the semiconductor substrate.